oracle/graal · error · IllegalArgumentException

Expected an espresso instance type as accessing class

Error message

Expected an espresso instance type as accessing class

What it means

Error "Expected an espresso instance type as accessing class" thrown in oracle/graal.

Source

Thrown at espresso-compiler-stub/src/com.oracle.truffle.espresso.vmaccess/src/com/oracle/truffle/espresso/vmaccess/EspressoExternalVMAccess.java:897

    private static Value lookupMetaObject(Context context, String name) {
        Value result = context.getBindings("java").getMember(name);
        JVMCIError.guarantee(result == null || result.isMetaObject(), "Unexpected result: %s", result);
        return result;
    }

    Value lookupMetaObject(String name) {
        return lookupMetaObject(context, name);
    }

    Value requireMetaObject(String name) {
        return requireMetaObject(context, name);
    }

    JavaType lookupType(String name, ResolvedJavaType accessingClass, boolean resolve) {
        Objects.requireNonNull(accessingClass);
        Objects.requireNonNull(name);
        if (!(accessingClass instanceof EspressoExternalResolvedInstanceType accessingInstantType)) {
            throw new IllegalArgumentException("Expected an espresso instance type as accessing class");
        }
        return lookupType(name, accessingInstantType, resolve);
    }

    EspressoExternalResolvedInstanceType getJavaLangObject() {
        return java_lang_Object;
    }

    EspressoExternalResolvedInstanceType[] getArrayInterfaces() {
        return arrayInterfaces;
    }

    JavaType lookupType(String name, EspressoExternalResolvedInstanceType accessingClass, boolean resolve) {
        JVMCIError.guarantee(!name.isEmpty(), "Name must not be empty");
        if (name.charAt(0) == '[') {
            int dims = 0;
            do {
                dims++;

View on GitHub (pinned to a66e9ccd1d)

Solutions

1. Fix the condition reported by the error: Expected an espresso instance type as accessing class
2. Check the throwing call site and ensure its documented preconditions (argument values, types, environment, or configuration) are satisfied before the call.

Example fix

Validate inputs and environment so that the failing condition does not occur: Expected an espresso instance type as accessing class

When it happens

Trigger: Thrown at espresso-compiler-stub/src/com.oracle.truffle.espresso.vmaccess/src/com/oracle/truffle/espresso/vmaccess/EspressoExternalVMAccess.java:897 when the library encounters an invalid state.

Common situations: Occurs when a caller violates the contract guarded by this check: Expected an espresso instance type as accessing class

AI-assisted analysis of oracle/graal@a66e9ccd1d (2026-08-14). Data as JSON: /api/errors/b36a6f5b2aa863de. Report an issue: GitHub.